Humphrey's inability to distinguish himself led to his spectacular defeat. The country was comfortable with Warren, and saw no reason to replace him.
What the voters did not know was that in 1962, Warren had ordered an explosive-metal bombattack on the Colonization Fleet while it was in orbit. Countless Race civilians were killed. This fact came to light in 1965. In response to an ultimatum from FleetlordAtvar, Warren agreed to allow the Race to destroy the city of Indianapolis in retribution, rather than discontinue the country's space program. Warren committed suicide shortly after Indianpolis was bombed. He was succeeded by Harold Stassen, who had, among other causes for concern, no confidence in his electability in 1968; he assumed the Democrats would capitalize on Warren's serious lapse of judgment and use it to leverage themselves into an electoral landslide.
In Worldwar, 1964 was a landslide victory for the Republicans; in OTL, it was a landslide for the Democrats. Of the four national candidates who ran in Worldwar, one was on the historical ballot: Hubert Humphrey ran for Vice President as the running mate of the incumbent Lyndon Johnson; there was no incumbent Vice President, the office had been vacant since Johnson ascended to the Presidency upon the death of John F. Kennedy. (Obviously, President Kennedy was the younger brother of Humphrey's Worldwar running-mate, Joe Kennedy Jr, who in true history had been killed in action during World War II. This is slightly ironic, as Humphrey had been a rival of both John and Robert Kennedy.) Warren's Worldwar running mate, Harold Stassen, had also sought the Republican presidential nomination, his fourth of what would ultimately be nine unsuccessful tries.
The Republican ticket was Barry Goldwater and William Miller. Goldwater ran a campaign that was lackluster to the point of listlessness, and lost by a humiliatingly wide margin: taking only six states to Johnson's 44 (plus the District of Columbia) and taking only 38.5% of the popular vote. However, Goldwater would become arguably the most influential political figure of his era, as his platform provided a blueprint for a conservative revival, known as neoconservatism, in the coming years. The popularity Johnson had enjoyed during the campaign quickly eroded as he served his full term, and he dropped out of the 1968 election in the face of stiff challenges for his own party's nomination. Republicans would win five of the next six elections, with veterans of Goldwater's campaign on the ballot each time.